This invention relates to especially designed and novel containers which have special structural features embodied therein for maintaining their sidewall integrity and, in particular, relates to the basal portion of plastic or thermoplastic container bodies that are so constructed so as to compensate against physical as well as chemical effects resulting in deviations in internal pressure after closing or sealing said bodies.
It is known that after filling and sealing a yieldable body such as a thermoplastic container there is a tendency for the sidewall thereof to deform or panel inwardly under certain conditions. This deformation of the sidewall results from deviations in pressure within the interior of the container as compared to the pressure in the exterior thereof and these deviations may be brought about by various physical or chemical conditions. In the packaging of food various materials including fluids such as juices, syrups, salad oils and the like are oftentimes brought to elevated temperatures before introduction into thermoplastic containers. It has been found that there is a marked tendency for such containers to incurve or distort inwardly due to changes in the internal and external pressure of such containers. For example, when hot-fill containers are allowed to cool, the internal pressure will gradually decrease whereby the external atmospheric pressure causes their sidewalls to indent, panel or otherwise partially collapse. Various attempts to rigidify or strengthen the sidewall configuration have been done to compensate for this tendency with various degrees of success.
Aside from the problems associated with such hot-fill containers there are other related packaging situations where chemical reactions cause noticeable reductions in the internal pressures of a container resulting in the paneling or deformation of the sidewall. For example, when lubrication or motor oil is packaged in a plastic container and sealed, chemical reactions take place between the various hydrocarbon constituents and any residual oxygen, e.g., air, causing the total pressure within the container to decrease. With this drop in pressure there results an inward paneling of the sidewall in order to equalize or compensate for the decrease in internal pressure. Here again, as with the hot-fill container, attempts have been made to provide rigidifying structures as well as containers with flexible features or components associated to compensate for this particular problem.
A number of prior art patents are known which relate to container structures that have flexible bottom portions that aid in pressure effects or have bottom endwall portions that appear structurally similar to those described and claimed herein. Although they are closely related, these prior art devices fall short of rendering an effective flexible member having the attributes of the subject invention. U.S. Pat. No. 1,570,732 to Emerson discloses a vacuum indicator device for sealed containers; U.S. Pat. No. 3,160,302 to Chaplin shows a container closure that is able to assume different positions depending upon the pressure conditions; U.S. Pat. No. 3,400,853 to Jacobsen teaches a container for filling hot goods, the container assuming a convex or concave position depending upon differential pressure application thereon; U.S. Pat. No. 4,099,475 and U.S. Pat. No. Des. 248,916 show an endwall structure somewhat similar to that disclosed and claimed herein; U.S. Pat. No. 3,409,167 discloses a container with a flexible bottom endwall structure; U.S. Pat. No. 3,426,939 to Young discloses a preferentially deformable container structure; U.S. Pat. No. 3,434,626 to Kinslow, Jr. teaches a plastic container bottom having increased strength and U.S. Pat. No. 4,134,354 to Cvacho, et al., discloses a metal container having a construction somewhat similar to the subject invention.
It will be appreciated that a paneled or deformed container would not have a desirable appearance from a marketing or consumer point of view. Aside from an undesirable appearance, the container itself loses column strength and sidewall symmetry which presents a problem in nesting or stacking them for storage, display and the like. Since the reduction in internal pressure cannot always be practically avoided, the subject invention provides a novel container configuration wherein a portion of the base of a container compensates or yields as more fully disclosed hereinafter in preference to the sidewall of a container.
The configuration of the container is so designed that it will displace or flex gradually through a series of positional displacements without affecting the integrity of the sidewall thereof. It will be appreciated hereinafter that the sidewalls are not made thicker than the base structure in order to achieve this goal but that the basal portion or the container is designed to flex. Of course, the degree of flexure will depend on the particular configuration of the various elements. In certain situations where chemical reactions continue to take place within a sealed container having entrapped air as, for example, where the air is gradually consumed by chemical reaction with unsaturated portions of the hydrocarbons, the flexing means will incurvate or distend inwardly to compensate for the gradual pressure drop and, as a result, the sidewall goes unaffected or undeformed.
The subject invention relates to an improved container having a non-paneling feature that can be manufactured with conventional machinery employed in thermoforming as well as scrapless forming processes and yet be consistent with strength and other requirements for containers.
Accordingly, an object of this invention is to provide a container body whose particularly designed bottom wall has improved bellowing ability as compared to conventional container structures.
An object of this invention is to provide containers profiled to be capable of preferentially adjusting pressure differences to a predetermined portion of the invention without deforming the sidewall and still rendering excellent serviceability.
Another object of this invention is to provide a configured bottom wall portion for thermoplastic containers that permits the bottom wall thereof to deform inwardly in preference to the sidewall of the container and yet maintain a strength characteristic commensurate to thermoplastic containers formed from relatively thicker stock materials.
Another object of this invention is to provide a plastic container having a configuration that has load-bearing properties substantially in balance with one another.
Still another object of this invention is to provide a container body having a structural design without overly constructing any individual feature thereof, the total structure providing optimum utilization of thermoplastic materials.
Another object of this invention is to provide the art with a yieldable bottom and for a container formed from scrapless forming techniques or thermoforming processes that have equalized or substantially equalized pressure adjusting portions.
A still further object of this invention is to provide the art with a multilayered container having a flexible bottom wall member wherein the container base flexes in preference to the container walls.
Other objects and advantages of this invention will be apparent to those skilled in the art from an inspection of the drawings, description and claims herein.